In general, road salts are used in order to increase the road safety on winterly roads. An important parameter for the organization of winter road maintenance as well as for the required quantity of the road salt to be spread is the freezing temperature on the road. According to the prior art the freezing temperature is detected by a sensor system installed in the road. This sensor system comprises, for instance, electrodes by means of which the conductivity of the water or water-ice mixture on the road and, thus, the salt content is sensed. Then, based on the salt content, the freezing temperature is determined. According to another approach an aqueous salt solution is actively cooled, and the freezing temperature is determined on the basis of the detected enthalpy jump.
However, the installation and maintenance of the sensor system calls for a great amount of work and disruptions of the traffic flow due to the road closure required for the installation and maintenance. Moreover, the installed sensor system provides information about the freezing temperature merely locally and for a relatively small area.
The present invention is based on the object to overcome the aforementioned drawbacks of the conventional freezing temperature determination and to provide a local or non-local reliable freezing temperature determination on winterly roads.